Nicholas Institute for Environmental Policy Solutions
February 2014

Greenhouse Gas Mitigation Opportunities for California Agriculture: Minimizing Diet Costs and Enteric Methane Emissions from Dairy Cows

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Greenhouse Gas Mitigation Opportunities for California Agriculture: Minimizing Diet Costs and Enteric Methane Emissions from Dairy Cows
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The study aimed to determine baseline methane emissions from California dairies and assess mitigation strategies. Two optimization models based on linear programming were developed to formulate minimum cost and minimum methane diets without compromising production. A third model uses weighted goal programming for joint minimization of dietary costs and emissions. The economic and environmental impact of using a specific agent (monensin) was also assessed. Enteric emissions ranged from 18.8 to 25.1 MJ/d. Dairies that used corn/alfalfa-based forages and cows with higher intakes and production were low emitters. The cost per unit emissions reduction ranged from $5.02 to $20.1/kg methane ($239–  $956/tonne CO2 equivalent) for a 1% to 25% reduction of total emissions. Various levels of trade-offs between cost and emissions reduction are possible. Up to a 9.4% reduction in CH4 emissions was possible with monensin (costs ranged from $3 to $26/kg CH4). Mitigation options need to be tested in a commercial setting before recommendation for use.